A GacS deficiency does not affectPseudomonas chlororaphisPA23 fitness when growing on canola, in aged batch culture or as a biofilm

2006 ◽  
Vol 52 (12) ◽  
pp. 1177-1188 ◽  
Author(s):  
N Poritsanos ◽  
C Selin ◽  
W G.D Fernando ◽  
S Nakkeeran ◽  
T.R. de Kievit
Keyword(s):  
Antifungal Activity ◽  
Batch Culture ◽  
Hydrogen Cyanide ◽  
Fungal Pathogen ◽  
Biocontrol Agent ◽  
Antifungal Compounds ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Biocontrol Activity ◽  
Competition Assays

Pseudomonas chlororaphis PA23 is a biocontrol agent that protects against the fungal pathogen Sclerotinia sclerotiorum. Employing transposon mutagenesis, we isolated a gacS mutant that no longer exhibited antifungal activity. Pseudomonas chlororaphis PA23 was previously reported to produce the nonvolatile antibiotics phenazine 1-carboxylic acid and 2-hydroxyphenazine. We report here that PA23 produces additional compounds, including protease, lipase, hydrogen cyanide, and siderophores, that may contribute to its biocontrol ability. In the gacS mutant background, generation of these products was markedly reduced or delayed with the exception of siderophores, which were elevated. Not surprisingly, this mutant was unable to protect canola from disease incited by S. sclerotiorum. The gacS mutant was able to sustain itself in the canola phyllosphere, therefore, the loss of biocontrol activity can be attributed to a reduced production of antifungal compounds and not a declining population size. Competition assays between the mutant and wild type revealed equivalent fitness in aged batch culture; consequently, the gacS mutation did not impart a growth advantage in the stationary phase phenotype. Under minimal nutrient conditions, the gacS-deficient strain produced a tenfold less biofilm than the wild type. However, no difference was observed in the ability of the mutant biofilm to protect cells from lethal antibiotic challenge.Key words: Pseudomonas, biocontrol, gacS, fitness, biofilms.

scholarly journals Altering the Ratio of Phenazines in Pseudomonas chlororaphis (aureofaciens) Strain 30-84: Effects on Biofilm Formation and Pathogen Inhibition

2008 ◽  
Vol 190 (8) ◽  
pp. 2759-2766 ◽  
Author(s):  
V. S. R. K. Maddula ◽  
E. A. Pierson ◽  
L. S. Pierson
Keyword(s):  
Fungal Pathogen ◽  
Biofilm Formation ◽  
Flow Cell ◽  
Gaeumannomyces Graminis ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Initial Attachment ◽  
Pathogen Inhibition ◽  
Biofilm Development ◽  
Derivatives Of

ABSTRACT Pseudomonas chlororaphis strain 30-84 is a plant-beneficial bacterium that is able to control take-all disease of wheat caused by the fungal pathogen Gaeumannomyces graminis var. tritici. The production of phenazines (PZs) by strain 30-84 is the primary mechanism of pathogen inhibition and contributes to the persistence of strain 30-84 in the rhizosphere. PZ production is regulated in part by the PhzR/PhzI quorum-sensing (QS) system. Previous flow cell analyses demonstrated that QS and PZs are involved in biofilm formation in P. chlororaphis (V. S. R. K. Maddula, Z. Zhang, E. A. Pierson, and L. S. Pierson III, Microb. Ecol. 52:289-301, 2006). P. chlororaphis produces mainly two PZs, phenazine-1-carboxylic acid (PCA) and 2-hydroxy-PCA (2-OH-PCA). In the present study, we examined the effect of altering the ratio of PZs produced by P. chlororaphis on biofilm formation and pathogen inhibition. As part of this study, we generated derivatives of strain 30-84 that produced only PCA or overproduced 2-OH-PCA. Using flow cell assays, we found that these PZ-altered derivatives of strain 30-84 differed from the wild type in initial attachment, mature biofilm architecture, and dispersal from biofilms. For example, increased 2-OH-PCA production promoted initial attachment and altered the three-dimensional structure of the mature biofilm relative to the wild type. Additionally, both alterations promoted thicker biofilm development and lowered dispersal rates compared to the wild type. The PZ-altered derivatives of strain 30-84 also differed in their ability to inhibit the fungal pathogen G. graminis var. tritici. Loss of 2-OH-PCA resulted in a significant reduction in the inhibition of G. graminis var. tritici. Our findings suggest that alterations in the ratios of antibiotic secondary metabolites synthesized by an organism may have complex and wide-ranging effects on its biology.

scholarly journals Comparative Genomic Analysis of Pseudomonas chlororaphis PCL1606 Reveals New Insight into Antifungal Compounds Involved in Biocontrol

2015 ◽  
Vol 28 (3) ◽  
pp. 249-260 ◽  
Author(s):  
Claudia E. Calderón ◽  
Cayo Ramos ◽  
Antonio de Vicente ◽  
Francisco M. Cazorla
Keyword(s):  
Genome Sequence ◽  
Genomic Analysis ◽  
Comparative Genomic Analysis ◽  
Whole Genome Sequence ◽  
Comparative Genomic ◽  
Antifungal Compound ◽  
Antifungal Compounds ◽  
Pseudomonas Chlororaphis ◽  
Biosynthetic Genes ◽  
Biocontrol Activity

Pseudomonas chlororaphis PCL1606 is a rhizobacterium that has biocontrol activity against many soilborne phytopathogenic fungi. The whole genome sequence of this strain was obtained using the Illumina Hiseq 2000 sequencing platform and was assembled using SOAP denovo software. The resulting 6.66-Mb complete sequence of the PCL1606 genome was further analyzed. A comparative genomic analysis using 10 plant-associated strains within the fluorescent Pseudomonas group, including the complete genome of P. chlororaphis PCL1606, revealed a diverse spectrum of traits involved in multitrophic interactions with plants and microbes as well as biological control. Phylogenetic analysis of these strains using eight housekeeping genes clearly placed strain PCL1606 into the P. chlororaphis group. The genome sequence of P. chlororaphis PCL1606 revealed the presence of sequences that were homologous to biosynthetic genes for the antifungal compounds 2-hexyl, 5-propyl resorcinol (HPR), hydrogen cyanide, and pyrrolnitrin; this is the first report of pyrrolnitrin encoding genes in this P. chlororaphis strain. Single-, double-, and triple-insertional mutants in the biosynthetic genes of each antifungal compound were used to test their roles in the production of these antifungal compounds and in antagonism and biocontrol of two fungal pathogens. The results confirmed the function of HPR in the antagonistic phenotype and in the biocontrol activity of P. chlororaphis PCL1606.

scholarly journals Antifungal activity in thrips soldiers suggests a dual role for this caste

2012 ◽  
Vol 8 (4) ◽  
pp. 526-529 ◽  
Author(s):  
Christine Turnbull ◽  
Holly Caravan ◽  
Thomas Chapman ◽  
David Nipperess ◽  
Siobhan Dennison ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Fungal Pathogen ◽  
Fungal Pathogens ◽  
Social Insect ◽  
Antifungal Compounds ◽  
Response To Selection ◽  
Male And Female ◽  
The Social ◽  
Selective Agents ◽  
Micro Organisms

The social insect soldier is perhaps the most widely known caste, because it often exhibits spectacular weapons, such as highly enlarged jaws or reinforced appendages, which are used to defend the colony against enemies ranging in size from wasps to anteaters. We examined the function of the enlarged forelimbs of soldiers (both male and female) of the eusocial, gall-inhabiting insect Kladothrips intermedius , and discovered that they have little impact on their ability to repel the specialized invading thrips Koptothrips species. While the efficacy of the enlarged forelimb appears equivocal, we show that soldiers secrete strong antifungal compounds capable of controlling the specialized insect fungal pathogen, Cordyceps bassiana . Our data suggest that these thrips soldiers have evolved in response to selection by both macro- and micro-organisms. While it is unknown whether specialized fungal pathogens have been major selective agents in the evolution of the soldier caste in general, they were probably present when sociality first evolved and may have been the primordial enemies of social insects.

scholarly journals Repression of the Antifungal Activity of Pseudomonas sp. Strain DF41 by the Stringent Response

2011 ◽  
Vol 77 (16) ◽  
pp. 5635-5642 ◽  
Author(s):  
Jerrylynn Manuel ◽  
Chrystal Berry ◽  
Carrie Selin ◽  
W. G. Dilantha Fernando ◽  
Teresa R. de Kievit
Keyword(s):  
Antifungal Activity ◽  
Fungal Pathogen ◽  
Protease Activity ◽  
Biological Control Agent ◽  
Stringent Response ◽  
Control Agent ◽  
Wild Type ◽  
Content Type ◽  
Guanosine Tetraphosphate ◽  
Maximum Expression

ABSTRACTThe stringent response (SR) enables bacteria to adapt to nutrient limitation through production of the nucleotides guanosine tetraphosphate and guanosine pentaphosphate, collectively known as (p)ppGpp. Two enzymes are responsible for the intracellular pools of (p)ppGpp: RelA acts as a synthetase, while SpoT can function as either a synthetase or a hydrolase. We investigated how the SR affects the ability of the biological control agentPseudomonassp. strain DF41 to inhibit the fungal pathogenSclerotinia sclerotiorum(Lib.) de Bary. Strain DF41relAandrelA spoTmutants were generated and found to exhibit increased antifungal activity. Strain DF41 produces a lipopeptide (LP) molecule that is essential forSclerotiniabiocontrol. LP production and protease activity were both elevated in therelAandrelA spoTmutants. Addition ofrelAbut notspoTintransrestored the mutant phenotype to that of the parent. Next, we investigated whether an association exists between the SR and known regulators of biocontrol, including the Gac system and RpoS. AgacSmutant of strain DF41 produced less (p)ppGpp and exhibited a 1.7-fold decrease inrelAexpression compared to the wild type, suggesting thatrelAforms part of the Gac regulon. We discovered thatrpoStranscription was reduced significantly in the SR mutants. Furthermore,rpoSprovided intransrestored protease activity to wild-type levels but did not attenuate antifungal activity. Finally,relAexpression was decreased in the mutants, indicating that the SR is required for maximum expression ofrelA.

scholarly journals Increased Antifungal Activity of Trichoderma harzianum Transformants That Overexpress a 33-kDa Chitinase

1999 ◽  
Vol 89 (3) ◽  
pp. 254-261 ◽  
Author(s):  
M. Carmen Limón ◽  
José A. Pintor-Toro ◽  
Tahía Benítez
Keyword(s):  
Antifungal Activity ◽  
Trichoderma Harzianum ◽  
Southern Blotting ◽  
Biocontrol Agent ◽  
Chitinase Activity ◽  
Restriction Pattern ◽  
Constitutive Promoter ◽  
Wild Type ◽  
Amds Gene ◽  
Culture Supernatants

Transformants of the biocontrol agent Trichoderma harzianum strain CECT 2413 that overexpressed a 33-kDa chitinase (Chit33) were obtained and characterized. Strain CECT 2413 was cotransformed with the amdS gene and its own chit33 gene under the control of the pki constitutive promoter from T. reesei. Southern blotting indicated that the chit33 gene was integrated ectopically, mostly in tandem. Some transformants showed the same restriction pattern, indicating preferable sites of integration. There was no correlation between the number of integrated copies and the level of expression of the chit33 gene in the transformants. When grown in glucose, the extracellular chitinase activity of the transformants was up to 200-fold greater than that of the wild type, whereas in chitin, the activity of both the transformants and the wild type was similar. Under both conditions, the transformants were more effective in inhibiting the growth of Rhizoctonia solani as compared with the wild type. Similar results were obtained when culture supernatants from the transformants and the wild type were tested against R. solani.

Quorum sensing and the anaerobic regulator (ANR) control Polyhydroxyalkanoate (PHA) production in Pseudomonas chlororaphis PA23

2019 ◽  
Author(s):  
Nisha Mohanan ◽  
April Gislason ◽  
Parveen K Sharma ◽  
Akrm Ghergab ◽  
Jocelyn Plouffe ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Minimal Medium ◽  
Biocontrol Agent ◽  
Antifungal Compounds ◽  
Pseudomonas Chlororaphis ◽  
Promoter Regions ◽  
Consensus Sequences ◽  
Energy Sink ◽  
Pha Production

Abstract Pseudomonas chlororaphis PA23 is a biocontrol agent that, in addition to producing antifungal compounds, synthesizes polyhydroxyalkanoate (PHA) polymers as a carbon and energy sink. Quorum sensing (QS) and the anaerobic regulator (ANR) are required for PA23-mediated fungal suppression; however, the role of these regulators in PHA production is unknown. Strains lacking either QS or ANR accumulated less PHA polymers when propagated on Ramsay's Minimal Medium (RMM) with glucose or octanoate as the carbon source. In the AHL-deficient background, all six of the genes in the pha locus (phaC1, phaC2, phaZ, phaD, phaF, phaI) showed reduced expression in RMM-glucose, and all except phaC2 were repressed in RMM-octanoate. While changes in gene activity were observed in the anr mutant, they were less pronounced. Analysis of the promoter regions for QS- and ANR-binding consensus sequences revealed putative phz-boxes upstream of phaZ and phaI, but no anr-boxes were identified. Our findings indicate that altered pha gene expression likely contributes to the lower PHA accumulation in the QS- and ANR-deficient strains, which may be in part indirectly mediated. This study is the first to show that mcl-PHA production is under QS and ANR control.

Hydrogen cyanide produced by Pseudomonas chlororaphis O6 is a key aphicidal metabolite

2019 ◽  
Vol 65 (3) ◽  
pp. 185-190 ◽  
Author(s):  
Beom Ryong Kang ◽  
Anne J. Anderson ◽  
Young Cheol Kim
Keyword(s):  
Hydrogen Cyanide ◽  
Type Strain ◽  
Wild Type Strain ◽  
Green Peach Aphid ◽  
Potassium Cyanide ◽  
Direct Application ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Production Of Hydrogen ◽  
Aphicidal Activity

A biocontrol bacterium, Pseudomonas chlororaphis O6 promotes plant health through multifaceted mechanisms. In this study, we used P. chlororaphis O6 mutants to examine metabolites with aphicidal activity. Direct application of intact P. chlororaphis cells to the surface of second-instar nymphs of the green peach aphid resulted in no mortality. However, nymphs died when exposed only to the volatiles produced by the P. chlororaphis O6 wild-type strain grown on rich media. Mutants lacking the production of two antibiotics, phenazine and pyrrolnitrin, or the insect toxin FitD retained the aphicidal potential of the wild-type strain. However, the volatiles produced by mutants deficient in the production of hydrogen cyanide (HCN) or defective in the synthesis of the global regulator GacS, which regulates HCN synthesis, showed no aphicidal activity. Direct application of potassium cyanide caused mortality of green peach aphid nymphs. These results indicate that HCN production by a plant probiotic is involved in preventing insect growth.

scholarly journals Biocontrol by Phenazine-1-carboxamide-Producing Pseudomonas chlororaphis PCL1391 of Tomato Root Rot Caused by Fusarium oxysporum f. sp. radicis-lycopersici

1998 ◽  
Vol 11 (11) ◽  
pp. 1069-1077 ◽  
Author(s):  
Thomas F. C. Chin-A-Woeng ◽  
Guido V. Bloemberg ◽  
Arjan J. van der Bij ◽  
Koen M. G. M. van der Drift ◽  
Jan Schripsema ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Fusarium Oxysporum ◽  
Root Rot ◽  
Test System ◽  
Pseudomonas Chlororaphis ◽  
Tomato Root ◽  
Hydrophobic Compound ◽  
Biocontrol Activity ◽  
In Vitro Antifungal Activity

Seventy bacterial isolates from the rhizosphere of tomato were screened for antagonistic activity against the tomato foot and root rot-causing fungal pathogen Fusarium oxysporum f. sp. radicis-lycopersici. One isolate, strain PCL1391, appeared to be an efficient colonizer of tomato roots and an excellent biocontrol strain in an F. oxysporum/tomato test system. Strain PCL1391 was identified as Pseudomonas chlororaphis and further characterization showed that it produces a broad spectrum of antifungal factors (AFFs), including a hydrophobic compound, hydrogen cyanide, chitinase(s), and protease(s). Through mass spectrometry and nuclear magnetic resonance, the hydrophobic compound was identified as phenazine-1-carboxamide (PCN). We have studied the production and action of this AFF both in vitro and in vivo. Using a PCL1391 transposon mutant, with a lux reporter gene inserted in the phenazine biosynthetic operon (phz), we showed that this phenazine biosynthetic mutant was substantially decreased in both in vitro antifungal activity and biocontrol activity. Moreover, with the same mutant it was shown that the phz biosynthetic operon is expressed in the tomato rhizosphere. Comparison of the biocontrol activity of the PCN-producing strain PCL1391 with those of phenazine-1-carboxylic acid (PCA)-producing strains P. fluorescens 2-79 and P. aureofaciens 30-84 showed that the PCN-producing strain is able to suppress disease in the tomato/F. oxysporum system, whereas the PCA-producing strains are not. Comparison of in vitro antifungal activity of PCN and PCA showed that the antifungal activity of PCN was at least 10 times higher at neutral pH, suggesting that this may contribute to the superior biocontrol performance of strain PCL1391 in the tomato/F. oxysporum system.

scholarly journals Fungal–bacterial interaction selects for quorum sensing mutants with increased production of natural antifungal compounds

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Andrea G. Albarracín Orio ◽  
Daniel Petras ◽  
Romina A. Tobares ◽  
Alexander A. Aksenov ◽  
Mingxun Wang ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Quorum Sensing ◽  
Fungal Pathogen ◽  
Antifungal Compounds ◽  
Environmental Strain ◽  
Sensing System ◽  
Bacterial Interaction ◽  
Quorum Sensing System ◽  
Genome Analyses ◽  
Setophoma Terrestris

AbstractSoil microorganisms coexist and interact showing antagonistic or mutualistic behaviors. Here, we show that an environmental strain of Bacillus subtilis undergoes heritable phenotypic variation upon interaction with the soil fungal pathogen Setophoma terrestris (ST). Metabolomics analysis revealed differential profiles in B. subtilis before (pre-ST) and after (post-ST) interacting with the fungus, which paradoxically involved the absence of lipopeptides surfactin and plipastatin and yet acquisition of antifungal activity in post-ST variants. The profile of volatile compounds showed that 2-heptanone and 2-octanone were the most discriminating metabolites present at higher concentrations in post-ST during the interaction process. Both ketones showed strong antifungal activity, which was lost with the addition of exogenous surfactin. Whole-genome analyses indicate that mutations in ComQPXA quorum-sensing system, constituted the genetic bases of post-ST conversion, which rewired B. subtilis metabolism towards the depletion of surfactins and the production of antifungal compounds during its antagonistic interaction with S. terrestris.

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